Re: Reduction in WAL for UPDATEs

"Zeugswetter Andreas ADI SD" <ZeugswetterA(at)spardat(dot)at> writes:
> Btw: Do we consider the existance of toasted columns in the seq-scan
> cost estimation ?

Not at present. There was some discussion of this but it seems like
a fair amount of work --- we don't currently track statistics on how
many of a column's entries are toasted or how big they are. For that
matter it would be entirely unreasonable to pin the cost on "seq scan";
you'd need to look in close detail at exactly where and how the Vars get
used, and distinguish simply copying a Var from actual use of its value.
The planner is mostly uninterested in the evaluation costs of plan node
targetlists at the moment, and IIRC that's something not so easily
changed...

regards, tom lane